Jeff Barr's book on AWS is a very readable howto and a quick way to get started with EC2, S3, CloudFront, CloudWatch and SimpleDB. It is short on theory, but long on all the details of really getting your hands dirty. Learn how to:

get started using the APIs to spinup servers

create a load balancer

add and remove application servers

build custom AMIs

create EBS volumes, attach them to your instances & format them

snapshot EBS volumes

use RAID with EBS

setup CloudWatch to monitor your instances

setup triggers with CloudWatch to enable AutoScaling

I would have liked to see examples in Chef rather than PHP, but hey you can't have everything!